Effect of Internal Architecture on the Elasticity of Microgel Monolayers at the Air/Water Interface

Soft microgels can deform and adsorb at liquid interfaces, forming monolayers with tunable compressibility and elasticity. Their deformabilityor softnessis governed by the internal architecture and inhomogeneity of the polymeric network. However, establishing a direct correlation between single-particle properties and their collective interfacial behaviorssuch as self-assembly and mechanical responseremains a fundamental challenge. In this work, we employ core-shell microgels with controllable internal architectures to investigate how single-particle softness influences the elasticity of microgel monolayers at the air/water interface. Flory-Rehner analysis reveals that microgel softness is determined by internal architecture via elastic free energy, with mixing contributions nearly invariant, ultimately governing osmotic deswelling behavior. Application of a generalized Hertzian potential in the semidilute regime further reveals enhanced chain entanglement within the confined interfacial polymer layer. Moreover, by analyzing the relationship between interparticle interactions and nearest neighbor distance in the condensed regime, we quantify the interfacial elasticity of the monolayers. Our findings show that microgels with loosely or homogeneously cross-linked networksrather than those with dense-core or dense-shell structuresyield higher elasticity. This counterintuitive result suggests that softer microgels can produce stiffer monolayers, which is further examined through the modulation of environmental and solution-related parameters.